Bandwidth on demand (BOD) in a satellite communication is advantageous because it makes more efficient use of the finite uplink resources of the satellite and correspondingly increases uplink capacity and useable bandwidth. Bandwidth efficiency, and in particular uplink bandwidth efficiency, is important when determining the profitability of a satellite communication system. Downlink efficiency generally becomes an issue when uplink efficiency approaches 100 percent.
A number of BOD satellite communication systems have been proposed. In a conventional BOD satellite system, a pre-assigned number of contention channels and data channels are configured by the system operator and are permanently assigned until they are reconfigured. Such a design is disadvantageous because the demand for contention channels can change. A satellite communication system using such a design makes less efficient use of the uplink bandwidth because contention channels could be used for data traffic when the demand for contention channels is low.
Other conventional BOD-type communication systems support only constant bit rate requests. User terminals requesting a constant bit rate are allocated permanent portions of a data channel until the user terminal requests that the allocation be terminated. A user terminal needing uplink bandwidth to send a file therefore requests a certain bit rate, sends the file, and then sends a de-allocation message to terminate the allocation. This approach is disadvantageous because of the increased messaging to set-up and de-allocate temporary channels which could otherwise be used for less bursty type traffic.
Conventional bandwidth on demand communication systems generally assign bandwidth in response to a bandwidth request via a single allocation. Thus, if the entire bandwidth request could not be satisfied, the user terminal would have to make additional bandwidth requests to obtain an allocation for the unsatisfied portion of the previous bandwidth requests.
A need therefore exists for a BOD communication system that efficiently processes the allocation and de-allocation of various sized bit rate requests, as well as volume-type requests for more bursty traffic. A BOD communication system is also needed to overcome the other disadvantages of conventional systems described above such as the dynamic use of channels as either data channels or contention channels. A need also exists for a BOD communication system which packs uplink data channels more efficiently to accommodate temporary bit rate requests, that is, volume requests for bursty traffic as well as constant bit rate requests and provide different grades of quality of service. A need also exists for a BOD communication system which generates a plurality of bandwidth allocations to satisfy a bandwidth request on a periodic basis rather than providing a requesting satellite terminal with whatever bandwidth is available at the moment and requiring the satellite terminal to re-request the allocated portion of the bandwidth request.